Come April 5, AMD are set to release the next entry in the HD 6000 series, the Radeon HD 6790. AMD has been keeping this info quite close to their chest, but the HD 6790 is set to compete against the green team's GeForce GTX 550 Ti.
The HD 6790 is based on AMD's 40nm "Barts" GPU (which the HD 68x0 share also). The Barts silicon is configured to have 800 stream processors (SPs), but it will be split across two blocks of 400 SPs each, each block having its own dispatch processor.
The core will be set at 840MHz, 1050MHz (4.2GHz effective) on memory which will provide 134.5GB/s memory bandwidth. The 6790 is expected to have a TDP of under 150W and will draw power from dual 6-pin power connectors.